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Bedrock is the solid rock at or below the land surface. Over much of Ireland, the bedrock is covered by materials such as soil and gravel. The Bedrock map shows what the land surface of Ireland would be made up of if these materials were removed. As the bedrock is commonly covered, bedrock maps are an interpretation of the available data.
Geologists map and record information on the composition and structure of rock outcrops (rock which can be seen on the land surface) and boreholes (a deep narrow round hole drilled in the ground). Areas are drawn on a map to show the distribution of rocks.
The Geological Lines layer shows the details of the structural geology; faults, folds and unconformities. Faults and folds are the result of great pressure being applied to rock across a whole continent or more. These rocks will either break under the pressure, forming faults, or they will bend to form folds. Faults are recorded in the Geological Lines layer as lines where the break in the rock meets the surface. Folds are shown only using the lines of their axes, synclinal (where the rock folds downwards) and anticlinal (where the rock folds upwards). Unconformities are where there is a gap in the rock record, typically where rock has been eroded away in the past and a new rock deposited on top.
Geologists map and record information on the structural geology. Lines are drawn on a map to show the location and extent of these structures.
The structural symbols layer is used to describe the geology of an area through dip and strike information. Dip and strike describe the behaviour of the rock bedding plane. To describe a geometric plane two values are required; the angle from horizontal that it is dipping and the direction that it is dipping. Geologists describe the dip direction by the strike value; this is the azimuth perpendicular to the steepest dip of the plane.
The measurements that this layer contains give information about the geometry of the rock units under the ground. These measurements are the only way to see if the rocks are folded and faulted and how. With this information we can also start to see why the rocks have the shapes that they do.
To produce this dataset, the twenty one 1:100,000 paper maps covering Ireland were digitised and borders and overlaps between map sheets were removed. We collect new data to update our map and also use data made available from other sources.
This map is to the scale 1:100,000. This means it should be viewed at that scale. When printed at that scale 1cm on the map relates to a distance of 1km.
It is a vector dataset. Vector data portray the world using points, lines, and polygons (areas).
The bedrock data is shown as polygons. Each polygon holds information on the rock unit name, its description, stratigraphy code (rock layers with age profile), lithology code (rock type) and map sheet number. Each polygon is linked to the bedrock lexicon table which has more detailed information such as a definition of the rock unit, rock types, age, thickness and other comments.
The geological line data is shown as lines. Each line holds information on: description of the line, bedrock 100k map sheet number, style and label information. Other information if relevant such as name, stratigraphy code (rock layers with age profile) & lithology code (rock type). Each line is linked to the bedrock linework lexicon table which has more detailed information such as a definition of the rock unit, rock types, age, thickness and other comments.
The structural symbols data is shown as points. Each point holds information on: the dip angle and direction, the strike angle and a description.
The outcrop data is shown as polygons.